The NIMH Collaborative Program on Psychobiology of Depression addresses two major substantive areas: 1) Nosology: To evaluate the comparative validity of alternative systems for clinical classification. 2) Genetics: To evaluate recent hypotheses that genetic factors are involved in the evolution of certain types of depressive disorders. In addition, this study also addresses a variety of other areas, including personality factors, life events, social supports, sociodemographic variables, and phenomenology. In addition to the comprehensive genetic study, family history variables are investigated in each proband. Finally, a large-scale follow-up investigation will also be completed on each subject.